This invention related to a coupling element for connecting two parallel shafts extending dehind one another, and having a transverse spacing between them. A coupling element of this type for shafts that are disposed with a fixed transverse spacing between them is known from DE-733 932.
In certain applications, it is necessary for the height of one shaft to be changed relative to a fixed reference plane, while the other shaft maintains its defined position relative to the reference plane. The problem encountered here is that both shafts must rotate in the same direction, and particularly at the same rpm, despite the adjustable alteration of the height relative to the reference plane, and the coupling element is not permitted to effect a fluctuation in rpm for the driven shaft.
An example of an application such as this is a piston-type internal-combustion engine with an alterable combustion chamber, in which the combustion chamber is altered by a raising or lowering of the crankshaft axis of rotation relative to a reference plane.
This kind of piston-type internal combustion engine is known from DE-36 44 721-A; in this case, the aforementioned problem is solved by securing a bearing housing, into which a driving pinion that is connected to the crankshaft extends at one end and, at the other end, a driven pinion that is connected to the driven shaft extends, to an adjusting cam for changing the height of the crankshaft. The axis of rotation of the adjusting cam coincides with the axis of rotation of the driven pinion. Forces are transmitted between the driving pinion at the crankshaft and the driven pinion through a pair of coaxially-rotating wheels, one of which rolls onto the driving pinion, while the other rolls onto the driven pinion. With this arrangement, any height adjustment can be made without rotational irregularities being imposed upon the power take-off. The drawback of the arrangement, however, is that space is only available for small gear diameters, so the entire torque of the piston-type internal-combustion engine must be transmitted by way of gears with a small diameter. This quickly results in limits in the magnitude of the transmittable torque. In addition, the tooth forces must be absorbed as reaction forces by way of a corresponding seating in the immediate vicinity of the gear. A further disadvantage of the arrangement is its relatively long structural length.
It is the object of the invention to create a coupling element that solves the problems of an adjustable shaft seating, and can be used to transmit large torques, and, at the same time, has a short structural length and can also be used to connect a crankshaft of a piston-type internal-combustion engine to a driving shaft.
According to the invention, this object is accomplished by a coupling element for connecting two shafts extending parallel to an axis, one behind the other, on the same axis and having a transverse spacing between themselves, in which the height of one shaft can be adjusted relative to a fixed reference plane through parallel-axis movements on a rotational path whose diameter corresponds to the maximum transverse spacing, with two rotating bodies that are oriented in parallel rotational planes and can be-connected to the respective associated shaft ends, and are provided, at equal radial distances from the respective axis of rotation, with bearing bores, and with crank elements that connect the two rotating bodies and whose crank radius corresponds to the transverse spacing between the shafts; the crank elements are disposed equidistantly one behind the other in the circumferential direction. With this type of coupling element, it is possible to set arbitrary heights of the shafts moving toward one another parallel to the same axis, within the predetermined eccentricity e; it is ensured here-that the rpm of the driving rotating body is transmitted to the driven rotating body by way of the crank elements without any rpm fluctuations. The dimensioning of the crank elements in the rotating bodies makes them suitable for transmitting the maximum torque. In addition to a corresponding dimensioning, the number of crank elements on one or more different partial rotational paths of the maximum transmittable torque can be increased. A particular advantage of the coupling element of the invention is that no restoring forces act on the bearings of the rotating bodies. This is especially significant in an application in a motor crankshaft.
Corresponding to the torque to be transmitted, it is possible in principle to provide a plurality of crank elements over the circumference of the rotating bodies, in which case the crank elements can be seated with their crank axes on different radii in the associated rotating bodies. In a particularly advantageous embodiment of the invention, it is provided that crank elements are arranged in groups, which, when seen in the circumferential direction, have the same circumferential angle relative to one another. In piston-type internal-combustion engines in which the crankshaft can be adjusted with respect to the stationary driven shaft in the engine housing, this type of grouped arrangement allows for consideration of the firing intervals of the respective internal-combustion engine. This attains an optimum support of the crank elements. Because the effective paths of the transmission forces are parallel in the direction of the connection of the cam center line, the effective lever arm changes with the rotation of the coupling element, so the effective lever arm of the cranks changes periodically from 0 to r, that is, it changes at the crank radius, and can assist proportionally in the transmission of the torque.
In an advantageous embodiment of the invention, it is also provided that the crank element is formed by a first and a second cylindrical body, whose axes are offset from one another. This results in a very short crank element. The arrangement can be such that the cylinders have the same diameter. It is advantageous, however, for the first cylindrical body of the crank element to have a larger diameter than the second cylindrical body, in which instance the second cylindrical body extends inside the outer circumference of the first cylindrical body, and projects beyond it in the axial direction on at least one side. It is advantageous for the region of the first cylindrical body that is not covered by the second cylindrical body to be provided with a recess that reduces an imbalance. The recess can be dimensioned such that the mass xe2x80x9cmissingxe2x80x9d from the first cylindrical body in the form of the recess approximately corresponds to the mass of the second cylindrical body.
For the tilt-free transmission of the torque from the driving rotating body to the driven rotating body, it is provided in a preferred embodiment of the invention that one rotating body, preferably the driven rotating body, has two disk parts, which are fixedly connected to one another with spacing, and the other rotating body, preferably the driving body, is embodied in a disk shape, and the crank elements are respectively seated in the two disk parts of the one rotating body, on the one hand, and in the rotating body located between them, on the other hand. This is possible with a crank element of the above-described type in accordance with the invention, in which a cylindrical body having a smaller diameter than the first cylindrical body projects beyond the first cylindrical body on both sides. A crank element embodied in this manner is seated with its first cylindrical body in the rotating body located between the two disk parts, while the second cylindrical bodies, which have the smaller diameter and are disposed eccentrically with respect to the axis of rotation of the first cylindrical body having the large diameter, are seated in the two disk parts of the other rotating body. A double-seated crank element of this type yields a tilt-free transmission of the torque.
It is especially advantageous for the first rotating body to be fixedly connectable by one disk part to the stationary shaft, and rotatably seated with its other disk part on a stationary support disposed coaxially to this shaft, so this first rotating body is also double-seated, and therefore permits a tilt-free torque transmission.